The invention relates to an electrical contact arrangement that is impervious to moisture and is disposed in a sealed area.
Contacts according to the species are well known in the automobile industry, for example in ignition systems. For example, the contacts between the distributor and the ignition cable, or between the ignition cable and spark plugs, are easily accessible and may be easily tested for tightness, for example by the vehicle user or by a repair shop. The seal is an essential requirement especially in the high-voltage area to ensure that there is no penetrating moisture which could cause short circuits and arcing which in turn could lead to a malfunction of the corresponding electrical system.
However, the tightness test described above is performed by separating the two contacts from one another. There is thus the disadvantage that tightness testing cannot be performed when the two contacts are in their assembled state. After the test described above, even if this test has shown previous tightness of the contact arrangement, the seal of the connection between the two components containing the two contacts may be impaired by contamination during reassemblyxe2x80x94with the result that each tightness test itself entails the risk of creating a leak.
The tightness test described is commonly performed during a diagnostic procedure in which it is sufficient to gain the information that the contact arrangement was, for example, tight in the past and thus may be eliminated as a source of the fault. Contacts according to the species are thus unsuitable for a manufacturer, for example, who wishes to determine whether or not a contact arrangement within a deliverable module has the required seal.
The object of the invention is to improve a generic contact arrangement such that it enables reliable testing of the contact arrangement for imperviousness to dust and moisture while eliminating both damage to the sealing means and the need to open the sealed space containing the contacts for testing.
This object of the invention is achieved by the following teachings.
The invention proposes providing two sealing elements, one of which seals off the contact arrangement from the environment. A test area is created between these two sealing elements which are located a certain distance from one another, said test area being accessible from the outside. In this way, an overpressure or underpressure relative to ambient pressure may be applied in this test area. The sealing elements therefore need not be contacted during testing, with the result that any risk of damage is averted. The sealed area containing the contacts remains closed during the test.
Since the entire module, including sealing elements, remains in its assembled state, a meaningful test result is obtained; no dislocations, deformations, or other effects on the sealing elements can occur following testing.
If the applied test pressure changes, even if it does not approach the ambient pressure, it may be assumed that the inner seal is damaged, i.e. the sealing element that adjoins the space in which the two contacts are located. The change in the test pressure results from the equalization of pressure between the test area and the space in which the two contacts are located.
To ensure reliable tightness of the modules to be delivered, the detected lack of tightness may thus result in the tested module""s being rejected.
Given this type of imperfect seal, the test result may indicate that at least the outer seal is sufficient since the equalization of pressure occurred only between the test area and the sealed space. If the opening of the test area accessible from outside is now sealed, for example by filling it with an adhesive or by inserting a sealing plug, the possibility of a leak through this test opening may be excluded with a high degree of probability and the entire contact arrangement may be shipped as a module which is sealed at this level of probability.
On the other hand, if, when the test pressure is applied, there is a change in pressure in which the test pressure reaches ambient pressure, it may be assumed that the external seal adjacent to the external environment is not tight. In this case, no meaningful information on the tightness of the inner seal may be obtained. To be conservative, the entire contact arrangement has to be considered not sealed, then repaired before it is once again tested and either rejected or shipped.
Each contact may be advantageously contained within its own component, the two components being plugged into each other. This approach permits a comparatively simple and cost-effective, as well as reliable design for the seals.
Here it is particularly advantageous if the plug of one component and the corresponding receptacle hole of the other component each have a round contour since it is then possible to use inexpensive, commercially available sealing rings, and it is also easier to create a reliable seal than it is with polygonal sealing contours.
Commercially available O-rings may be used to particular advantage, these O-rings being proven and reliable sealing elements, as well as inexpensive and commercially available.
An electrically conductive connection between the two contacts may be achieved simply and inexpensively by a spring, for example a compression spring, located between the two contacts and compensating for any axial play between the two components or between the two contacts. A spring designed as a helical or coil spring can, by deforming, achieve an immediate compensation in length between the two contacts, said spring always acting on the contacts at the same points. A flat spring connected electrically with the one contact and located laterally adjacent to the other contact can compensate for the axial play of the contacts even without deformation by contacting the other contact at different points. In this way, a reliable connection between the two contacts is ensured by the spring independently of manufacturing tolerances or movements during operation of the component, for example due to vibrational excitations.
One embodiment of the invention is described in more detail below based on the drawing.
Here, 1 indicates a first component which consists of an electrically insulating material, for example plastic. Within first component 1 is located first contact 2 which forms a sleeve with two sections. A lower section 3 with a smaller diameter serves to accommodate and guide compression spring 4 which is designed as a helical spring. Upper section 5 with a larger diameter accommodates second contact 6.